$(document).ready(function(){
	goTopEx();
	$("#dain").click(function(){
		$(".xianshi").show();
	})
})
function goTopEx() {
				var obj = document.getElementById("goTopBtn");
				function getScrollTop() {return document.documentElement.scrollTop + document.body.scrollTop;}
				function setScrollTop(value) {
					if (document.documentElement.scrollTop) {
						document.documentElement.scrollTop = value;
					} else {
						document.body.scrollTop = value;
					}
				}
				window.onscroll = function() {
					getScrollTop() > 0 ? obj.style.display = "" : obj.style.display = "none";
				}
				obj.onclick = function() {
					var goTop = setInterval(scrollMove,2);
					function scrollMove() {
						setScrollTop(getScrollTop() / 1.1);
						if (getScrollTop() < 1) clearInterval(goTop);
					}
				}
			}
